As photographers we are always enticed to buy more and more gadgets, be they lenses, flashes, lights, modifiers, filters, software, triggers, tripods, bags etc etc and of course they all make our photography better, even though they usually get left in the bag if they even make it that far!
Well here is one gadget that I'm glad I bought, and it's a few years now since I got it, December 2010 to be exact, and with cameras like the D800 producing files of over 36mb it's proving more valuable. 
It's a Portable Photo/Video Storage device. Mine is the Nexto ND2700, also referred to as eXtreme, see here for details. An old link at this stage but it gives you all the details of how it works. It is really useful when travelling and answers the question of how will I store my images while I'm away from home. Will I bring numerous cards, or a laptop/netbook, and additional external storage or all three. When I travel I like to make it light and bring as little as possible and this device weights only 240g and measures 127mm x 76mm x 22mm, barely bigger than the 160gb 2.5" SATA hard drive I have in it. Of course you can put in a bigger drive if you wish. To back up your card all you need to do is insert your card into one of the two slots. One slot for CF cards and another for SD/SDHC/MMC/MS/xD devices. Via the USB port you can also connect your Card Reader, Video or Camera. You simply either copy or move your files across which the system will verify and it is very fast, my 16gb CF card takes about 5-7 minutes to copy and verify. You cannot see the images but the LCD panel will show you the file structures and what files are on it.
To get your images off the storage device on to your computer you connect via the USB or eSATA port. I also use it to back up my video files. The ND2700 cost me about €210 from Amazon but it has now been superseded by the ND2700 on which you can see your images on the colour LCD as well as other technical updates. Nexto also provide professional solutions for video backup. Their websites are not the greatest but that is probably due to translation from Korean, their American web site is http://www.nextodi.com/ and their UK website: http://nextodi.co.uk/.
There are different devices out there try Adorama or B&H Video Photo.